Interpretive Summary: We have developed a simple, species nonspecific, and accurate protocol for the quantification of thermotolerance. Acquired thermotolerance is induced by pre-exposure to elevated but non-lethal temperatures and leads to enhanced protection of plant cells from subsequent heat induced injury. Our protocol is based on the inhibition of chlorophyll accumulation in etiolated tissue by challenges at lethal temperatures and the prevention o this inhibition by preincubation at a non-lethal elevated temperature; i.e., acquired thermotolerance. Arabidopsis thaliana mutants deficient in varying levels of acquired thermotolerance have been identified from both the RLD and Columbia ecotypes and these mutants are currently undergoing a detailed characterization at both the protein and molecular levels.

Technical Abstract:
Plants experience high air and soil temperatures during periods of drought and when fields receive limited irrigation. Elevated plant temperatures that occur under these conditions negatively impact plant health and productivity. Plants, like all organisms, respond to an elevation in temperature by the synthesis of heat shock proteins (HSPs). The appearance eof plant HSPs is strongly correlated to the development of a condition termed "acquired thermotolerance". Acquired thermotolerance is induced by pre-exposure to elevated but non-lethal temperatures and leads to enhanced protection of plant cells from subsequent heat induced injury. To understand the relationship between HSPs and acquired thermotolerance, mutations would be required that result in a coordinate change in the expressions of HSPs. This paper describes the history of our research efforts on acquired thermotolerance leading to the development of screening gprocedures for the isolation and characterization of acquired thermotolerance mutants. We have developed a simple, species nonspecific, reliable, and accurate protocol for the quantification of thermotolerance. This protocol is based on the inhibition of chlorophyll accumulation in etiolated tissue by challenges at lethal temperatures and the prevention of this inhibition by preincubation at a non-lethal elevated temperature; i.e., acquired thermotolerance. Arabidopsis thaliana mutants deficient in varying levels of acquired thermotolerance have been identified from both the RLD and Columbia ecotypes and these mutants are currently undergoing a detailed characterization at both the protein and molecular levels.